The first thing he parses is this: the boy can sing.

The second is that this is the history of the Sodder family, which brightens the interest in his very dark eyes. Orpheus stops to explain, and John claps (very quietly, because it's a library; he thinks this is funny).

"No, I'm with you." He gestures a little hurry up motion, a little go on. "I follow. Got any more?"